1. Field of the Invention
The present invention relates to a nonaqueous electrolyte battery containing nonaqueous solvent as solvent of an electrolyte thereof.
2. Related Background Art
A lithium secondary battery containing nonaqueous electrolyte incorporates a positive electrode which is usually constituted by applying, to aluminum foil, metal oxide and the like serving as an active material for the positive electrode. Moreover, a negative electrode of the battery is constituted by crimping, to copper foil, lithium serving as an active material for the negative electrode. In addition, a separator constituted by a finely-porous film made of polyethylene is disposed between the two electrodes obtained as described above. A coil constituted by winding and stacking the obtained structure is accommodated in a can made of stainless steel and serving as an external electrode (for example, an external negative electrode).
The above-mentioned lithium secondary battery has characteristics of a large capacity, high voltage and a large output. If the circuit or the like under abnormal conditions causes the positive electrode and the negative electrode of the battery to be short-circuited, the temperature of the battery is undesirably raised. To prevent rise in the temperature of the battery, a variety of protective means, such as a temperature fuse, an electric current fuse and a PTC device are provided for the battery. In addition, a safety valve for preventing rise in the pressure in the battery is provided.
However, a variety of abnormal states are assumed to occur as well as the short circuit of the positive electrode and the negative electrode of the battery caused from an abnormal state of the circuit in the battery. If the battery is crushed by external pressure by accident, the separator between the positive electrode and the negative electrode is broken or melted. Thus, the positive electrode and the negative electrode are short-circuited. If the positive electrode and the negative electrode are short-circuited, there is apprehension that the battery is damaged by heat, smoke or the like.